Means for forming integral finned tubing



May 9, 1961 w. H. LABAN MEANS FOR FORMING INTEGRAL FINNED TUBING Filed Dec. 31, 1958 2 Sheets-Sheet 1 F/GZ.

R M MH YTMN MN R EE 0 WW M A m Y W B May 9, 1961 Mia W m NN 0 EE HV. "H M A m w W MnANs'FoR FORMING INTEGRAL 7 FINNED TUBING Laban, West Hagley, England, assignoi' to' Accles &Pollock Limited, Birmingham, England, a British company I Filed Dec. 31, 1958, Ser. No. 784,206

Claims priority, application Great Britain Jan. .6, 1958 3 Claims. (CI. 8013) This invention relates to the formation of integral ex-. ternal fins or ribs around tubes, by subjecting a' tube to the action of forming rolls or discs to extrude or displace from the metal of the tube wall an integral fin or rib, which may be of a helical form, three rolls, for example, being spaced'equi-distantly around a tubular blank in rolling contact therewith, with the axes of the rolls, where the fin is to be of a helical form, at a slight angle to the axis of the tube according to the pitch or helix angle of the tin which is to be developed. Such fin forming rolls have previously been either in the form of cylindrical bodies formed around their peripheries with a plurality of annular portions of various cross-sectional shapes, or they have consisted of a plurality of discs disposed closely together side by side and rigidly clamped together, to rotate as a single unit, by suitable means.

Considerable difliculties arise in the manufacture of integral finned tubing, particularly when deep finning is attempted, for example, on steel tubes, such ditficulties being due mainly to excessive roll wear and to roll breakage, and to tearing or breaking away of the fins themselves. Roll breakage is frequently due to spreading of the tube wall along the face of the roll when applying high pressure to the bottom of the groove. Such roll breakages are more likely during the final stages of the fin development where the annular portions of the rolls are necessarily deeper and generally less robust.

Also, since corresponding tip and root diameters of the fins and of the engaging annular portions of the rolls are ditferent, par-ts of the contacting side surfaces of the same move at diiferent speeds, causing slip and, with high pressure against the sides of the fins, considerable friction results, with consequential roll wear and high heat and power losses. Fin tearing is particularly liable to occur when forming very thin fins owing to the axial or lateral pressures which are exerted against the sides of the fins during the later stages of their development.

2 portions of the positively driven primary. tin-developing roll, so that the peripheries of the freely mounted discs do not engage the bottom of thegroove already formed between the fin convolutions, and thus, in use, not only on, and exert pressure only on, the sides of the fin.

Figure 'l of the accompanying drawings is a diagrammatic cross-sectional view showing the disposition of i 1 tube 3. The rolls are adapted to be moved radially into.

three fin-forming rolls in relation to the tube on which helical fin is being developed.

Figure 2 is a longitudinal section through one of the rolls according to the present invention.

Figure 3 is. a sectional view on a larger scale through a portion of the roll shown in Figure 2.

Figure 4 is a longitudinal section showing a modified form of roll in accordance with the invention.

' Referring to Figures 1 to 3 of the drawings, a plurality of rolls are employed, in known manner, for the formation of an integral helical fin around a metal tube. In the arrangement shown diagrammatically in Figure 1, three rolls 1 are shown, each mounted on a driving shaft 2 and spaced at equal angular distances apart around the rolling contact with the tube, and the axes of the shafts 2 are disposed at a slight angle to the axis of the tube, according to the helix angle of .the fin that is to be formed, so that the tube is advanced axially during the development of the fin.

The three rolls are similar or substantially similar and only one will therefore be described. In the construction shown each roll comprises a primary roll member mounted on the shaft 2 and which includes a solid substantially first part 4 formed around its periphery with a plurality of integral annular parts or ribs 5 separated by grooves 6, and a second part made up'of a plurality of separate discs 7 rigidly clamped together and to the aforesaid positively-driven first part to rotate therewith and with the shaft 2. The clamping is effected by means of ;a spacer ring slidable at the shaft and pressed against the discs 7 by means of a nut 9 so as to clamp said rings and the solid part 4 against a collar 10 on the shaft. The annular ribs of the solid part 4 and of the discs 7 are of a substantially square section with parallel sides, but they increase progressively in diameter, providing between them annular parallel-sided grooves of progressively increasing depth, the diameters of the parts which form the bottoms of the grooves, at the same time, becoming progressively smaller. The heights of the ribs on the part 4 are preferably kept small to avoid any tendency for It is the object of the present invention to minimise the above disadvantages as far as possible.

According to the invention, means for use in the formation of an integral external fin'or rib around a metal tube, by extrusion or displacement of the metal, comprises at least one freely-mounted or floating roll or disc, rotated solely by rotation of the tube around which the fin or rib is being formed. A plurality of loosely-mounted freely-rotatable discs disposed side by side and driven by the tube may be used for the completion of the fin or rib, the initial development of the fin and the rotation of the tube being obtained by a positively driven roll unit. The loosely-mounted freely-rotatable discs may be slightly spaced apart, and their peripheral fin or rib developing portions may, for example, have oppositely-inclined sides; or freely rotatable discs may be disposed close together and their annular portions formed on opposed faces with annular shoulders which exert pressure on the sides of the partly-formed fin which is radial, or substantially radial, to theaxis of the tube. The freely rotatable discs may be of diameters smaller than the diameters of the annular them to break ofi. The clampedtogether discs 7 may. be all of the same diameter, the outer peripheral portions of the said discs being narrower than the main body portions of the discs to form ribs or annuli 11 having like wise fiat parallel sides which join the main body portions of the discs, these body portions being formed with an-' nular shoulders, so that the said flat-sided annuli 11, which are of ya square section at their peripheries, with rounded corners, provide between them deep flat-sided grooves, the latter being deeper than the grooves separating the grooves 6 between the annular ribs 5 of the first part 4 of the primary roll. latter is made up of the separately-formed clampedtogether discs 7 as a matter of convenience, so that they may be readily replaced, if necessary, but they may, if desired, be formed solid'or integral with the first part 4 of the primary roll.

. Mounted on the spacer ring 8, so that they may freely rotate thereon, is a plurality of-loose floating discs 12 laterally separated from one another by small clearances, as at .13. These loose or floating discs may have peripheral annuli 14 all of a simialr cross-sectional shape, and the said discs are all of diameters less than the diameters of I the clamped-together discs 7 forming the second, part of Patented May 9, 1961 The aforesaid second part of the 7 the primary roll, so that they do not, therefore reach to the bottom of the groove 15 formed in the tube wall by the clamped-together discs. Each of these freely rotatable floating discs 12Icomprises a main central body part with and the clamped-together discs 7 is positively driven by.

the shaft 2 independently of the tube 3 upon which it operates and which during the developmentof the fill-16.

is caused to rotate, but the loose floating discs 12, on the other hand, are arranged to be rotated solely by the tube.

'In' operation, the annular ribs of the first part 4 of the primary roll portion, and the peripheral parts 11 of the clamped-together discs 7, develop around the tube, by extruding the metal from the tube wall, a helical parallelsidedfin- 16 of a progressively increasing height or diameter. Since the sides of the annular ribs 5 of the first part of the roll and also the sides'ofthe operating peripheral. portions 11 of the clamped-together discs 7 are parallel, the metal is extruded into plain ring-grooves as quickly as possible, the pressure exerted on the tube wall being radial. The diameters of the annular rib parts 5 of the primary roll member and of the clamped-together discs 7 are such that they do not vary to any great extent and there is virtually no slip at the fin sides, excessive friction, with roll wear, heat and power loss, being-to a large ex tent reduced or eliminated, whilst the possibility of damage to the rolls is at the same time reduced. The spreading of the tube wall, and-the resulting loss due to roll breakage, should also be reduced, and the separate clamped-together discs 7 for the intermediate fin-forming stage may be arranged to spring slightly, sufliciently to permit of some spreading of the tube wall without breakage. The fin 16 is deepened and the outer portion of the fin is shaped by the free. floating discs 12, and as. the partlyformed fin passes from the clamped-together discs 7 to the loose or floating discs 12 the tapered outer portions of the latter are forced radially into the fin groove. Since the discs 12 are free to rotate, and are spaced slightly apart, they are free to float and to adapt themselves to that part of the fin groove opposite to which theyare opposed, automatically taking up proper positions, so that they exert equal pressures on'the opposite sides of the fin convolutions to finish the desired extruding and shaping action The discs 12' also adapt themselves to the speed of the tube by which they are rotated, thereby reducing tional numberof integral annular v.rilrportions totake 1 into the channels, the said 'roll member 17 being clamped against a collar on thetshaftby a spacer ring similar to the ring 8 in Figural and nut 9, so as to servelto complete the root shape of the fin 16. The sides of thetfin are finally shaped and a-refurther extruded byyfreely rotatable discs 19 which are loosely mounted upon the spacer ring,- as in FigureZ andaIe rotatedat aspe ed greater than that of the primary roll portion 17 by the tube itself. These freely rotatable discshave peripheral annuli 20 separated by grooves, but instead of these annuli being tapered or wedge-sectioned, ,theside faces of some of the said annuli are formed with .an annular stepped portion, or with a plurality of annular stepped portions, theremaining portions of the said side faces being straight and parallel. The said discs do not, therefore, exert such-a lateral pressure on the sides of the fin, as in the previously-described arrangement. All, of the floating discs 19 have their outer 'peripheral portions thinner than the main body portions,'which latter, in this case, fit closely together side by'side, without clearances,

. but so that they are free to turn independently on the any tendency toslip. At the sametime, the loose or floating discs only act on the sides of the fin, since they do not reach to the bottoms of the grooves, so that theydo not exert pressure on the body of the tube or on the root end of the fin. As there is no stress on the body of the tube there is no tendency for the latter to lengthen- The positively driven primary roll portion 4, with the clamped-together discs 7, rotate the tube by engaging the latter at their outer edges, at the fin base, and the tube then rotates the free or floating discs 12 through their engagement with the sides of the fin. The mean driving contact between the fin and the loose floating discs can be regarded. as being approximately on a circle near to the outer edge of the fin, which circle is of a diameter larger than that of the fin base, with the result that the loose or floating discs travel faster than the positively driven primary roll portion 4 and clamped-together discs 7, which is a considerable advantage; By the use of floating discs driven by the tube not only is an improved finish given to the completed fin, but friction is consid-' erably reduced and consequential deformation or't'earing of the fin -tip avoided. v g a If .de'sired, the primary roll portion 4 may have" an addispacer ring upon which they are mounted, the nut'9 merely serving to hold them loosely together without exerting any clamping action. The said'outer peripheral portions 20 are thus separated by narrow deep annular channels capable of receiving the partly formed-fin, the channels between successive annuli becoming progressively deeper, to permit of the fin being gradually extruded to a greater height or width. Theouter peripheral edges of all of the floating discs are of a rounded semi-circular section, and they do not extendup' to the root-end of the fin, so that there is no spreading action, the root end havingbeen completely shaped by the primary roll member. There are thus no loads imposed on the peripheral edges of the loose discs. I

The annulus of the first of the freely rotatable. discs has its one side, which is next to the primary member 17, straight without a shouldered portion, but its-opposite side, and the opposed side, of the second disc annulus, is formed near to the thicker body portion with a narrow annular shoulder 21, so that as the partly formed fin moves between the opposedfaces of the annuli of these two discs the shoulders 21, which may be inclined, exert a mainly radial and partly lateral pressure on the two sides of the outer edge or tip portion of the fin, compressing the same and extruding the metal to widen or deepen the fin. The other face of the second disc annulus, and the opposingface of the third disc annulus are likewise formed with similarly disposed annular shoul: der 21 but the sides are shaped so that they together form a deeper annular groove to receive the fin, which is now further deepened or vwdened. The other face of the third disc annulus and the opposing face of the next disc annulus are each formed with two annular shoulders 21 the shoulders on the two discs being immediately opposite to one another with one shoulderon each face nearer the outer peripheraledges of the discs than is the other shoulder. The action of. the third or fourth discs is thus to effect a furtherextrusion or widening of the fin. The opposed faces of the next pair of annuli are formed with three annular shouldered portions 21 the shoulders, however, .being'less prominent, whilst on the next pair of opposed faces there are three shoulders which are still less prominent, the surfaces of the discsbeing more or less of a wave-like form. The opposed faces of the remaining two annuli 22 are plain and these last finishing ann uli are of a basically wedge like section, and are provided on a single .wide disc 23. The annular shoulders on the disc annuli" draw out the 5 fin by a purely rolling action, thereby reducing friction and slip.

Any number of floating or freely rotatable discs driven by the tube being flanged may be provided, and the discs may be of any other cross-sectional shape, being however, preferably of such diameters that they act only on the sides of a partly formed flange, without engaging or exerting pressure upon the root ends of the tin, or against the bottom of the groove between the fin.

The freely rotatable or floating discs may be carried by a positively driven roll, as described, to form therewith a self-contained assembly, or they may be independent of the positively driven roll, if desired.

Instead of the floating discs being mounted on a spacer ring on the same-shaft as carries the primary roll member, as described, they may be mounted on a separate shaft, with the two shafts arranged, for example, in alignment, and the floating discs, mounted independently on their own shaft, may be brought into use at any desired stage of the tube finning operations.

I claim:

1. Means for developing an integral helical fin around a tube comprising a positively driven rotatable fin-developing primary roll unit having peripheral annular portions engageable with the tube to cause rotation thereof 25 2,720,801

and to initiate the formation of a groove therein, and a secondary roll unit for completing the fin-developing process, said secondary roll unit being composed of a plurality of loose and freely supported rotatable fin-developing discs having annular portions of wedge section, said discs being independently driven solely by the tube during the fin developing process and all of said discs having a diameter which is less than the maximum diameter of the annular portions of the primary roll unit, whereby the peripheries of the freely rotatable discs do not engage the bottom of the groove already formed between the annular portions of said primary roll unit.

2. Means for developing an integral helical fin upon a tube according to claim 1, wherein the primary roll unit and the secondary roll unit are disposed axially adjacent to one another, the primary roll unit being fixed to a driving shaft and the discs of the secondary roll unit being freely and independently rotatable relatively to said driving shaft and primary roll unit.

3. Means for developing an integral helical fin around a tube according to claim 1, wherein the loose discs have clearances between them.

References Cited in the file of this patent UNITED STATES PATENTS 1,865,575 Locke July 5, 1932 1,901,516 Hopkins 'Mar. 14, 1933 Erdelyi et a1. Oct. 18, 1955 FOREIGN PATENTS 111,528 Australia Sept. 12, 1940 

